--- url-cache.el	2006-05-06 18:32:00.000000000 -0400
+++ /home/happy/src/emacs/multi-tty/lisp/url/url-cache.el	2006-05-06 21:29:57.000000000 -0400
@@ -34,6 +34,12 @@
   :type 'directory
   :group 'url-file)
 
+;; If the cache file is large, we don't want to read the whole file just to
+;; get the headers
+(defvar url-cache-max-header-size 1024
+  "Number of bytes to read when looking for header in cache file.
+Used by `url-cache-get-header'.")
+
 ;; Cache manager
 (defun url-cache-file-writable-p (file)
   "Follows the documentation of `file-writable-p', unlike `file-writable-p'."
@@ -75,13 +81,29 @@
 
 ;;;###autoload
 (defun url-is-cached (url)
-  "Return non-nil if the URL is cached."
+  "Return non-nil if the URL is cached.
+If URL is cached return a list: '(lastmod etag)."
   (let* ((fname (url-cache-create-filename url))
-	 (attribs (file-attributes fname)))
-    (and fname				; got a filename
-	 (file-exists-p fname)		; file exists
-	 (not (eq (nth 0 attribs) t))	; Its not a directory
-	 (nth 5 attribs))))		; Can get last mod-time
+	 (attribs (file-attributes fname))
+	 (lastmod (and fname				; got a filename
+		       (file-exists-p fname)		; file exists
+		       (not (eq (nth 0 attribs) t))	; Its not a directory
+		       (nth 5 attribs)))		; Can get last mod-time
+	 (etag (and lastmod
+		    (url-cache-get-header "ETag" fname))))
+    (if (or lastmod
+	    etag)
+	`(,lastmod ,etag))))
+
+(defun url-cache-get-header (header file)
+  "Return value of HEADER from cache FILE.
+FILE must be a value returned by `url-cache-create-filename'.
+Reads up to `url-cache-max-header-size' bytes of the cache file.."
+  (if (file-exists-p file)
+      (with-temp-buffer
+	(insert-file-contents-literally file nil 0 url-cache-max-header-size)
+	(mail-narrow-to-head)
+	(mail-fetch-field "ETag"))))
 
 (defun url-cache-create-filename-human-readable (url)
   "Return a filename in the local cache for URL"
@@ -182,7 +204,8 @@
 (defun url-cache-extract (fnam)
   "Extract FNAM from the local disk cache"
   (erase-buffer)
-  (insert-file-contents-literally fnam))
+  (if (file-exists-p fnam)
+      (insert-file-contents-literally fnam)))
 
 ;;;###autoload
 (defun url-cache-expired (url mod)